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Barges and their towboats accumulate alongside the Mississippi banks of the Mississippi River near Greenville, Miss., Tuesday, Aug. 21, 2012. Officials with the U.S. Army Corps of Engineers say low water levels that are restricting shipping traffic, forcing harbor closures and causing towboats and barges to run aground on the Mississippi River are expected to continue into October. (AP Photo/Rogelio V. Solis)

U.S. drought crisis

Triple-digit temperatures and weeks without rain withered and destroyed many crops in the Midwest, sending commodity soybean and grain prices soaring in 2012.